1. Field of the Invention
The present invention generally relates to a heat treatment apparatus for heating a substrate such as a semiconductor wafer (hereinafter referred to as “a wafer”), and more specifically to a vertical heat treatment apparatus including a reaction tube, a heating section disposed around the reaction tube, a wafer holding section for holding a wafer in the reaction tube, and a supporting section movably provided in the vertical direction so that the wafer holding section can be put into and taken off from the reaction tube and provided so as to seal the reaction tube while the wafer holding section is disposed inside the reaction tube.
2. Description of the Related Art
As an example of a heat treatment apparatus for heating wafers, there has been known a vertical heat treatment apparatus capable of processing plural wafers as a batch process (see, for example, Japanese Patent Nos. 3116905 and 3378241).
FIG. 9 schematically shows a conventional vertical heat treatment apparatus.
The vertical heat treatment apparatus includes a reaction tube 21 for heating the wafer in the reaction tube 21. A heater 23 is provided around the reaction tube 21 for heating the reaction tube 21. A circular quartz flange 25 having substantially the same inner diameter as that of the reaction tube 21 is provided at the opening section of the reaction tube 21.
An SIC (Silicon carbide) boat 27 is provided to hold the wafers in the reaction tube 21. The SIC boat 27 is on a sealing cap 29 that is movably provided in the vertical direction, in a manner so that a base quartz section 31, a fin heat retaining tube 33, and an SIC heat retaining tube 35 are placed between the SIC boat 27 and the sealing cap 29.
The base quartz section 31 having a disk shape is on the sealing cap 29. The fin heat retaining tube 33 including quartz and having fins is on the base quartz section 31. The SIC heat retaining tube 35 is on the fin heat retaining tube 33, and the SIC boat 27 is on the SIC heat retaining tube 35.
When the sealing cap 29 is lifted up, the SIC boat 27 is in the reaction tube 21. Then, the upper surface of the sealing cap 29 is in contact with the quartz flange 25 to seal the reaction tube 21.
For example, when a vertical heat treatment apparatus for heating wafers for diffusing impurities has no temperature sensor to monitor a temperature, a temperature sensor using, for example, a thermocouple is required to be inserted in the reaction tube 21 to periodically measure a temperature profile or check the temperature in the reaction tube 21.
To that end, an insertion hole 29a for inserting a temperature sensor in the reaction tube 21 is previously provided in the sealing cap 29. On the other hand, there is no such insertion hole on the base quartz section 31 on the sealing cap 29 in view of the fact that chlorine gas may be used in the baking process. Due to this situation, to insert a temperature sensor into the reaction tube 21 as shown in FIG. 10, it is necessary to replace the base quartz section 31 with another base quartz section 37 on which a temperature sensor insertion section 37a is formed. Since the fin heat retaining tube 33, SIC heat retaining tube 35, and SIC boat 27 are placed on the base quartz section 31 to be replaced, it is also necessary to disassemble those parts when the base quartz section 31 is required to be replaced.
In addition, when the fin heat retaining tube 33, the SIC heat retaining tube 35, and the SIC boat 27 that have been disassembled are reassembled in their original positions, a position error due to the disassembling process may occur. Due to the caused position error, it becomes necessary to make adjustments of the mounting position of the SIC boat 27 and a transfer robot. The positions of the SIC boat 27 and the transfer robot should be adjusted before the SIC boat 27 is repositioned in the vertical heat treatment apparatus so as to avoid a situation where the SIC boat is in contact with a wafer while the wafer is being transferred.
In the adjustment operations, it is necessary to adjust in the front-to-back, side-to-side, and up-to-down directions of the transfer robot, and an offset adjustment of the transfer robot itself may also be necessary when the adjustment in the up-to-down direction is carried out. The time necessary for those adjustment operations varies depending on an operator's skill, but about one through three hours may typically be required. Further, when the base quartz section 31 is replaced by the base quartz section 37, not only an operation for replacing the base quartz section 31 by the base quartz section 37 but also the operations for detaching and attaching the fin heat retaining tube 33, the SIC heat retaining tube 35, and the SIC boat 27 are required. At least 30 minutes are typically required for those detaching and attaching operations.
Furthermore, during all the above operations of replacing the base quartz section 31 by the base quartz section 37 and detaching and attaching the fin heat retaining tube 33, the SIC heat retaining tube 35, and the SIC boat 27, an operator's hands are directly used. Because of this feature, there arises a concern about polluting the reaction tube 21 with “Na” and the like. Therefore, a baking process using chlorine gas is typically performed to eliminate the pollutant after the above operations.
As described above, there are disadvantages due to the disassembling operations necessary for inserting a temperature sensor into the reaction tube in a conventional vertical heat treatment apparatus.